feat: add status FIFO and parse status line in client

engine/src/looper.c

@@ -5,6 +5,9 @@
 #include "midi.h"
 #include "queue.h"
 #include <jack/jack.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
 #include <jack/midiport.h>
 #include <math.h>
 #include <stdatomic.h>
@@ -12,6 +15,39 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define STATUS_FIFO "/tmp/looper_status"
+
+static void looper_write_status(void) {
+    int fd = open(STATUS_FIFO, O_WRONLY | O_NONBLOCK);
+    if (fd < 0)
+        return;
+    struct channel_t *cur = get_channels_array();
+    int cap = atomic_load(&channel_capacity);
+    char buf[256];
+    for (int ch = 0; ch < cap; ch++) {
+        if (!atomic_load(&cur[ch].active))
+            continue;
+        int sc_idx = atomic_load(&cur[ch].current_scene);
+        int state = atomic_load(&cur[ch].scenes[sc_idx].state);
+        const char *state_str;
+        switch (state) {
+            case STATE_IDLE:    state_str = "IDLE";    break;
+            case STATE_RECORD:  state_str = "RECORD";  break;
+            case STATE_LOOPING: state_str = "LOOPING"; break;
+            case STATE_PAUSED:  state_str = "PAUSED";  break;
+            default:            state_str = "UNKNOWN";
+        }
+        int n = snprintf(buf, sizeof(buf),
+                         "CH=%d SC=%d STATE=%s\n",
+                         ch, sc_idx, state_str);
+        if (n > 0) {
+            int ret = write(fd, buf, n);
+            (void)ret;
+        }
+    }
+    close(fd);
+}
+
 /* Global state (shared across files) */
 struct channel_t *_Atomic channels = NULL;
 atomic_int channel_capacity = 0;
@@ -393,6 +429,9 @@ void jack_shutdown_cb(void *arg) {
  * looper initialisation
  * ---------------------------------------------------------------- */
 int looper_init(jack_client_t *client) {
+  /* create status FIFO (ignore if already exists) */
+  mkfifo(STATUS_FIFO, 0666);
+
   queue_init(&cmd_queue);
   queue_init(&cmd_queue_main_midi);
   queue_init(&cmd_queue_main_fifo);
@@ -631,4 +670,7 @@ void looper_process_commands(jack_client_t *client) {
       pending_old = NULL;
     }
   }
+
+  /* write current state to status FIFO */
+  looper_write_status();
 }